1. Field of the Invention
The present invention relates to a solid-state imaging apparatus and imaging system.
2. Description of the Related Art
An imaging system such as a digital camera can be downsized by using a solid-state imaging apparatus in which pixels for imaging each having a photoelectric conversion portion and pixels for focus detection having a photoelectric conversion portion are arranged on a single substrate. As each pixel for imaging, it is possible to use, for example, a pixel (a red, green, or blue pixel) obtained by forming a red, green, or blue color filter on the photoelectric conversion portion. These pixels for imaging can be arranged in accordance with, for example, a Bayer array, and the pixels for focus detection can be arranged in some of positions where, for example, the blue pixels are to be arranged. Normally, no color filter is formed in the pixel for focus detection in many cases.
An element isolation region can be formed between the pixels of the substrate so as to prevent crosstalk occurring when a signal charge generated in each pixel moves between adjacent pixels. As the number of pixels increases (as the size of each pixel decreases), however, it has become necessary to increase the photoelectric conversion efficiency of the photoelectric conversion portion and decrease the area of the element isolation region at the same time. This makes it difficult to suppress crosstalk.
In the structure of the above-described pixel array, the amount of crosstalk between, for example, the blue pixel and green pixel is different from that of crosstalk between the pixel for focus detection and the green pixel. This is so because a depth to which light having entered a pixel reaches from the substrate surface changes in accordance with wavelength of the light, that is, photoelectric conversion occurs when light having entered the photoelectric conversion portion of the pixel for focus detection reaches to a position deeper than that of blue light from the substrate surface, and an electric charge is generated in this deep position. Accordingly, the amount of electric charge moving from the pixel for focus detection to an adjacent green pixel, for example, becomes larger than that of electric charge moving from the blue pixel to an adjacent green pixel. Thus, in the arrangement in which the pixels for imaging and the pixels for focus detection are arranged on a single substrate, the amount of crosstalk in the region where the pixel for focus detection is arranged differs from that in other regions, and this may deteriorate the quality of an image to be obtained.